At present, in order to lower intra-cell interference in a Long Term Evolution (LTE) system, a common scheme is adopted to transmit data through Orthogonal Frequency Division Multiplexing (OFDM) on a downlink control channel, and despite lowered intra-cell interference, this scheme may significantly increase Inter-Cell Interference (ICI) particularly as compared with a traditional 3G system. In order to lower inter-cell interference, a common scheme is adopted to transmit data through frequency multiplexing across cells, that is, to use different frequency bands for networking between adjacent cells. For example, there is an available networking scheme with a frequency multiplexing factor of 3, 4 or 7; and this networking scheme poses a significant challenge to the LTE system with a maximum system bandwidth of 20 MHz, for example, given a networking bandwidth of 20 MHz, the LTE system has to provide a bandwidth of 60 MHz if a frequency multiplexing factor of 3 is adopted; the LTE system has to provide a bandwidth of 80 MHz if a frequency multiplexing factor of 4 is adopted; and the LTE system has to provide a bandwidth of 140 MHz if a frequency multiplexing factor of 7 is adopted. However the scarcity of existing frequency resources makes it rather difficult to provide the foregoing bandwidths.
A key to an implementation of same-frequency networking in the LTE system lies in the anti-interference performance of a downlink control channel, and the feasibility to implement same-frequency networking in the LTE system can be guaranteed only if the anti-interference performance of the downlink control channel in the LET system is ensured to be achieved as required. In a network with a specific number of users, there are typically numerous demands for scheduling of uplink and downlink shared channels, and given same-frequency networking, a Physical Downlink Control Channel (PDCCH) has a high probability of being subject to strong interference of an adjacent cell, so that there is serious same-frequency interference of the PDCCH channel, thus greatly limiting the performance of receiving data on the downlink control channel. Since scheduling and resource allocation information of the uplink and downlink shared channels is borne on a downlink control channel (e.g., a PDCCH channel), the performance of receiving data on the downlink control channel poses significant influence upon the Quality of Service (QoS) of a user service.
In the LTE system, uplink and downlink shared channels are typically scheduled in two scheduling schemes, which are dynamic scheduling and Semi-Persistent Scheduling (SPS) respectively, and these two scheduling schemes will be detailed below respectively.
For dynamic scheduling, an eNB has to notify a User Equipment (UE) of resource allocation information of a corresponding sub-frame in real time per Transmission Timing Interval (TTI) to make full use of a shared channel resource; and to provide the UE with a data transmission service in the dynamic scheduling scheme, the eNB sends allocation information of a resource allocated to the UE on a PDCCH: for a Physical Downlink Shared Channel (PDSCH), resource allocation information of the PDSCH is sent to the UE on the PDCCH of a sub-frame n; and the UE receives the corresponding PDCCH information in the sub-frame n and receives downlink data information at a corresponding location of the PDSCH of the sub-frame n according to an indication of the PDCCH information; and for a Physical Uplink Shared Channel (PUSCH), resource allocation information of the PUSCH is sent to the UE on the PDCCH of a sub-frame n−k (k=4 for a frequency division duplex system; and the value of k depends upon a sub-frame configuration and a sub-frame number for a time division duplex system). Since the resource allocation information indicated by dynamic scheduling signaling is validated only in the current sub-frame but invalidated in other sub-frames, the eNB can allocate the resource in the other sub-frames without instructing the UE to reclaim the resource.
In order to guarantee the QoS of a user service, the eNB performs dynamic scheduling by determining UEs to be scheduled for transmission of data and allocating resources capable of bearing the amount of data (i.e., the size of a Transport Block (TB)) for these UEs to be scheduled, where the TB size is determined by the level of a Modulation and Coding Scheme (MCS) determined and the number of resource blocks allocated by the eNB. A result of dynamic scheduling can vary in real time, so resources can be scheduled in the dynamic scheduling scheme for data services with distinct burst characteristics of the size of a data packet, a time of arrival of traffic data, etc. Although the dynamic scheduling scheme can improve a utilization ratio of the shared channel resource, an uplink scheduling grant or downlink resource allocation information has to be indicated in real time on the PDCCH, so there is a drawback of a considerable overhead of control signaling for the use of the dynamic scheduling scheme.
For semi-persistent scheduling, a Radio Resource Control (RRC) layer configures a corresponding UE with semi-persistent scheduling related parameters in RRC signaling, and the related parameters may include a Cell Radio Network Temporary Identity (C-RNTI), an uplink semi-persistent scheduling resource interval, a downlink semi-persistent scheduling resource interval, etc.; and a Media Access Control (MAC) layer of the eNB determines a semi-persistent scheduling resource to be activated for respective UEs, and upon determining a semi-persistent scheduling resource of a specific UE to be activated in a current sub-frame, a semi-persistent scheduling module allocates a corresponding resource by determining the locations and amount of the allocated resource, the amount of data that can be borne (a TB size, etc.), etc., and thereafter the UE is notified of activation information of the semi-persistent scheduling resource on a PDCCH channel scrambled with an SPS C-RNTI; and the UE determines from the semi-persistent scheduling resource intervals configured by the RRC layer the locations where the semi-persistent scheduling resource reoccurs (the locations can be as illustrated in FIG. 1 where boxes filled with slanted lines in FIG. 1 represent the configured semi-persistent scheduling resource) and transmits and receives data at the corresponding locations.
For an uplink shared channel, a semi-persistent scheduling resource can be deactivated by a UE on its own initiative, that is, released implicitly; and for uplink and downlink shared channels, a semi-persistent scheduling resource can be deactivated by an eNB on its own initiative. If the eNB determines that a specific UE using an active semi-persistent scheduling resource satisfies a condition to release the semi-persistent scheduling resource, the eNB can send an instruction on a PDCCH channel to deactivate the semi-persistent scheduling resource; and the UE will not transmit data or receive data periodically as per a configuration of semi-persistent scheduling any longer upon reception of the instruction sent from the eNB to deactivate the semi-persistent scheduling resource. In the LTE standard, semi-persistent scheduling is generally applicable to a service with both a fixed time of arrival of a data packet and a constant size of a data packet (e.g., a Voice over Internet Protocol (VoIP) service).
There is an insignificant demand of an UE for a PDCCH channel in transmission of data in the semi-persistent scheduling scheme, so an overhead of control channel signaling can be significantly saved; but in the existing LTE standard, if it is intended to reconfigure a semi-persistent scheduling resource interval, it has to be reconfigured in RRC signaling; and if it is intended to modify the size and location of a Physical Resource Block (PRB) resource, an MCS, a TB size or the like allocated for the UE, then they have to be indicated again on a PDCCH.
At present an eNB provides a UE with a data transmission service selectively through semi-persistent scheduling or dynamic scheduling dependent upon the type of a borne service, for example, the semi-persistent scheduling scheme for a VoIP service to save an overhead of control channel signaling, and the dynamic scheduling mechanism for other services (e.g., data services in the File Transfer Protocol (FTP), the Hyper Text Transfer Protocol (HTTP), Video Streaming, etc.) to improve a utilization ratio of a shared channel resource. Along with continued popularization of services, there are an increasing number of data services, and the use of the dynamic scheduling scheme has to be adopted for a large number of data services in the LTE system, so that there might be a serious load of a downlink control channel (e.g., a PDCCH channel) on which an uplink scheduling grant and downlink scheduling signaling is borne, thus resulting in serious inter-cell same-frequency interference to the downlink control channel with same-frequency networking in the LTE system, and consequently the problem of serious inter-cell same-frequency interference to the downlink control channel arising from a considerable overhead of control channel signaling may still exist with the use of the existing scheduling scheme.